The subject matter disclosed herein relates to the art of circuit breakers and, more particularly, to a filter assembly for a circuit breaker arc chamber.
Circuit breakers typically include a stationary contact and a movable contact. A switch assembly shifts or pivots the movable contact against the stationary contact to complete an electrical circuit. The switch assembly may also be operated to disengage the movable contact from the stationary contact to interrupt the electrical circuit. In addition to manual operation, circuit breakers include systems to open the electrical connection in the event of an over current condition. More specifically, circuit breakers are designed to interrupt current flow in the event that current levels exceed a predetermined rating. Often times when interrupting the electrical circuit due to an over current condition, breaking a connection between the movable contact and the stationary contact results in an arc. Many circuit breakers include an arc chamber that captures the arc.
Conventional arc chambers may include a filter to capture debris and gasses associated with arcing and degradation of the movable contact and/or the stationary contact that may occur. In conventional filters, a plurality of superposed wire cloths have progressive mesh openings; the cloth presenting the largest mesh openings is disposed to be the first cloth (i.e., upstream) being passed through by the gases, while the cloth presenting the smallest mesh openings, is disposed to be the last cloth (i.e., downstream) being passed through by the gases.
However, in some circuit breakers, the arcing generated when interrupting relatively high levels of current result in very high internal pressures generated within the circuit breaker housing. While internal pressure may help to extinguish an arc, however if the pressure is too high, damage to the integrity of the housing may result. Using prior art circuit breakers having conventional progressive arc filters can in certain instances generate undesired high internal pressures in the arc chamber, and result in damage to the wire mesh of the smallest mesh filter. Accordingly, there is a need for an improved arc filter assembly for a circuit breaker having an optimized screen or filter that cools the high temperature gasses, reduces gas and particulate egress from the circuit breaker housing, while reducing internal pressures during arcing conditions, and consequent damage to the filter.